From what I've seen, freight & passenger service don't work on the same tracks if passenger is > 80 or so. Very light freight service, mainly in off hours, can continue if passenger service is frequent at 90 or so, but can only continue as a main line if the passenger service at 90 is limited to a couple of trains a day. Dispatching trains that move 20-50mph more than the rest of the traffic is a nightmare. So yes, I think we will end up with a separate system for passengers if we're serious about hauling them, "high" speed or not, unless we're willing to settle for backwoods specials that trundle along at barely more than freight speed.

Now if 80-90 mph freight (again - remember the Super C?) could serve an economic need then perhaps something might change. IMO, if the HSR folk aren't seriously looking at overnight containerized (like for airplanes) freight then their system even under the best of assumptions is doomed. We'll know HSR is real when Amazon puts a warehouse/distribution center at a HSR station.